1. Field of the Invention
The present invention relates to a flat panel display device, and more particularly, to a flat luminescence lamp and method for manufacturing the same. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for reducing size of the lamp, thereby enhancing luminescence.
2. Discussion of the Related Art
An ultra thin flat panel display device has a display screen with a thickness of several centimeters. Especially, liquid crystal display (LCD) devices among the flat panel display device are widely used for monitors of notebook computers, spacecrafts, and aircrafts.
Of such LCDs, a passive luminescence LCD device has a backlight attached at the rear side of a liquid crystal panel and used as a light source. However, the backlight is generally inefficient in terms of weight, power consumption, and thickness.
The backlight used as a light source of an LCD is formed in such a manner that a cylindrical fluorescent lamp is arranged thereon. The backlight includes a direct type and a light-guiding plate type.
In the direct type backlight, a fluorescent lamp is mounted on a flat panel. Since a shape of the fluorescent lamp is displayed on a liquid crystal panel, it is necessary to maintain a certain distance between the fluorescent lamp and the liquid crystal panel and arrange a light-scattering means for a uniform light distribution. In this case, there is a limitation in forming a thin sized backlight.
Due to a trend of a large sized panel, a light-emitting area of the backlight increases. If the direct type backlight has a large area, the light-scattering means should have a sufficient thickness to make the light-emitting area flat. In this case, there is also a limitation in forming a thin sized backlight.
In the light-guiding plate type, a fluorescent lamp is mounted outside the flat panel so that light is dispersed in all sides using a light-guiding plate. In this case, since the fluorescent lamp is mounted at the side and light should pass through the light-guiding plate, a problem arises in that luminance is low. Also, for a uniform distribution of luminous intensity, an advanced optical design and processing technologies are required.
Currently, for high luminance, a direct type backlight has been proposed in which a number of lamps are arranged below the display surface or a lamp is arranged in a bent shape. Further, a flat luminescent backlight having a flat surface facing into the display surface of the panel, thereby illuminating from the entire surface has been researched and developed. This type of the flat luminescent backlight is disclosed in the U.S. Pat. No. 6,034,470.
A related art flat luminescent lamp will be described with reference to the accompanying drawings.
FIG. 1 is a plane view illustrating a related art flat luminescent lamp, and FIG. 2 is a cross-sectional view taken along the line II—II of FIG. 1.
As shown in FIG. 1, the related art flat luminescent lamp includes a lower substrate 11, an upper substrate 11a, cathodes 13 formed on the lower substrate 11, anodes 13a formed on the upper substrate 11a, four frames 19a, 19b, 19c, and 19d for sealing the lower and upper substrates 11a and 11 by a soldering such as a glass solder, and a plurality of support rods 21 formed between the lower and upper substrates 11 and 11a. 
More specifically, the anodes 13a are formed in pairs at constant intervals. The cathodes 13 are formed on the corresponding lower substrate 11 between the anodes 13a. The cathodes 13 and the anodes 13a are coated with a dielectric material, and an external voltage is applied to the cathodes 13 and the anodes 13a through a lead line.
Surfaces of the upper and lower substrates 11a and 11 facing into a discharge space are coated with a fluorescent material. In the discharge space, a Xe gas inducing discharge forms plasma and emits ultraviolet rays (UV). The emitted UV comes into collision with the fluorescent material on the upper and lower substrates 11a and 11. For this reason, the UV is excited to generate visible rays.
Additionally, a reflecting plate 14 (shown in FIG. 2) is further provided over the lower substrate 11. The reflecting plate 14 serves to prevent the visible rays generated in the discharge space from leaking out to the rear side of the lower substrate 11. The support rods 21 are made of a glass material so as not to interrupt emission of the visible rays.
Referring to FIG. 2, the cathodes 13 are formed on the lower substrate 11 of a glass material. A first dielectric material layer 12 is formed on the lower substrate 11 including the cathodes 13. The reflecting plate 14 is formed on the first dielectric material layer 12 and a first phosphor layer 15 is formed on the reflecting plate 14. The anodes 13a that induce discharge together with the cathodes 13 are formed on the upper substrate 11a of a glass material.
A second dielectric material layer 12a is formed on the upper substrate 11a including the anodes 13a. A second phosphor layer 15a is formed on the second dielectric material layer 12a. On the upper and lower substrates 11a and 11, frames 19a, 19b, 19c, and 19d are formed thereon to seal the upper and lower substrates 11a and 11 by a glass solder. It is well known that the cathodes 13 and the anodes 13a are formed by silk printing or a vapor deposition process.
In the aforementioned related art flat luminescent lamp, if a voltage is applied to the cathodes 13 and the anodes 13a through a lead line, a Xe gas forms plasma in the discharge space between the cathodes 13 and the anodes 13a, thereby emitting UV. In this process, the UV comes into collision with the first and second phosphor layers 15 and 15a to generate visible rays, so that the UV is emitted.
However, the related art flat luminescent lamp has several problems as follows.
Since the cathodes and the anodes are formed by silk printing or a vapor deposition process, there is a limitation in reducing the widths of the cathodes and the anodes at 0.2 mm (a minimum value) or below. Accordingly, luminous uniformity of the light-emitting area is deteriorated due to obscure rays near the cathodes and the anodes and discontinuity in plasma.